Since groundwater is a significant source of water for drinking, recreation and irrigation, its supply and purity are of paramount importance. Contaminants present as a constituent in groundwater can pose a significant risk, sometimes even in trace amounts. Therefore, groundwater monitoring for detecting the presence of contaminants is important in order to protect this source of water. In order to properly characterize a contaminant plume, a number of samples must be taken at different locations to ascertain how the concentration of the constituents vary from one location in a system to another and how they change over time. Since groundwater systems are three-dimensional and plume migration depends upon many factors, monitoring requires sampling each system at different locations in both the horizontal and vertical planes. Such multiple sampling in conjunction with hydrogeologic testing allows the evolution of a plume in an aquifer system to be predicted and thus, a remediation plan can be designed.
Contaminant vapors are sometimes concentrated in the vadose zone (non-saturated) when the plume is sufficiently high in concentration. These vapors may sometimes lead to explosion concerns or hazardous atmospheric conditions when they encounter confined spaces (i.e. basements, sewer lines, electrical conduits, etc.). Remediation of the is necessary in order to restore the entire environment to its prerelease condition and to prevent further contribution of contaminants to the groundwater through leaching of soils. Similar to groundwater plume monitoring, soil samples must be collected sufficiently to define a contaminated soil zone. After the contaminated soil zone is sufficiently defined, the soils must often be remediated. Excavation is not always cost effective, therefore the soil sometimes must be remediated through the use of soil vapor extraction.
Several different methods for providing access to multiple subsurface horizons for sampling, testing, and remediation exist as standard industry practice. One method employs installation of multiple monitoring wells, at varying depths to provide access to multiple subsurface horizons. A variation on this method would be the installation of several casings each to a different depth all within the same drilled borehole. Other methods of sampling groundwater at different depths are exemplified by U.S. Pat. Nos. 5,375,478 to Barnhardt; 5,293,931 to Nichols et al.; and 4,838,079 to Harris.
The present invention is directed to a subsurface casing well system which allows for adequate selective communication for the purposes of aquifer testing, sampling of fluids, and remediation through a single casing without the use of multiple boreholes or sampling ports.